Idiomelon

Idiomelon (Greek: idio, "unique" + melon, "melody"; Church Slavonic: samoglasen)—pl. idiomela—is a sticheron which originally had it's own tune, and did not follow that of any other.[1]
An idiomelon is assigned to one of the eight tones of Byzantine chant, is not patterned on any other hymn in terms of meter, content, or melody, and does not serve as a model or pattern for other hymns of the same textual category. These include, for example, stichera of the Resurrection, stichera of Great Feasts, etc. It melodically follows the schema of the tone and yet is usually eccentric in its metre.